Protein matrices are important for tissue function, tissue regeneration, wound healing, and hemostasis. For example many eukaryotic cells are enveloped by an extracellular matrix of proteins that provide structural support, cell and tissue identity, and autocrine, paracrine and juxtacrine properties for the cell and the matrix is thus required for normal tissue functions. In wound healing a cascade of molecular and cellular events initially leads to hemostasis, the prevention of blood loss. Fibrin plays a crucial role in hemostasis and wound healing as it forms a crosslinked proteinaceous matrix (clot) by means of a complex cascade of reactions with the final steps being the conversion of monomeric fibrinogen by thrombin, to form a crosslinked fibrin polymer, which is often referred to as a clot.
In addition to its role in hemostasis, fibrin formation is common in a number of pathological and inflammatory conditions. For example, abnormal fibrin deposition (thrombosis) is associated with atherosclerosis, rheumatoid arthritis, glomerulonephritis, systemic lupus erythematosus, myocardial infarcts, stroke, pulmonary embolism, deep vein thrombosis, autoimmune neuropathies, granulomatous disease, parasitic infections and allograft rejection. There is also evidence that thrombosis plays a role in neurodegenerative disease.
Protein matrices such as extracellular matrix and fibrin clots are typically dynamic, that is the matrix can be formed and degraded as part of pathological processes or normal physiological processes. Indeed, hemostasis can be viewed as the maintenance of equilibrium between the formation of fibrin clots (coagulation) and the proteolytic degradation of those clots (fibrinolysis) by factors including plasmin.
Methods for detection or monitoring of the formation of protein matrices such as blood clots (thrombi) include for example methods of determining blood coagulation e.g., prothrombin time, thrombin clotting time or the Clauss method for fibrinogen testing, and there are commercial devices that can perform such coagulation testing in portable, point-of-care formats. However, tests for detection or monitoring of proteolysis are typically limited to complex methods in specialized laboratories, such as, for example thromboelastometry (TEM), and are not applicable to point of care or field diagnostics. Other methods use colorimetric or fluorescent detection methodologies and are, too, expensive, complex and are negatively affected by the color or turbidity of a sample.
There exists a need for methods, apparatus and systems for detection and/or monitoring of proteolysis of protein matrices. In particular, detection of fibrinolytic activity in the blood can be a valuable medical diagnostics tool.